Abstract
Simple SummaryThe irradiation of tumors involving the eye or orbit represents a complex therapeutic challenge due to the proximity between the tumor and organs that are susceptible to radiation. The challenges include tumor control, as it is often a surrogate for survival; organ (usually the eyeball) preservation; and the minimization of damage of sensitive tissues surrounding the tumor in order to preserve vision. Anticipation of the spectrum and severity of radiation-induced complications is crucial to the decision of which technique to use for a given tumor. The aim of the present review is to report the non-cancer effects that may occur following ionizing irradiation involving the eye and orbit and their specific patterns of toxicity for a given radiotherapy modality. The pros and cons of conventional and advanced forms of radiation techniques and their clinical implementation are provided with a clinical perspective.The eye is an exemplarily challenging organ to treat when considering ocular tumors. It is at the crossroads of several major aims in oncology: tumor control, organ preservation, and functional outcomes including vision and quality of life. The proximity between the tumor and organs that are susceptible to radiation damage explain these challenges. Given a high enough dose of radiation, virtually any cancer will be destroyed with radiotherapy. Yet, the doses inevitably absorbed by normal tissues may lead to complications, the likelihood of which increases with the radiation dose and volume of normal tissues irradiated. Precision radiotherapy allows personalized decision-making algorithms based on patient and tumor characteristics by exploiting the full knowledge of the physics, radiobiology, and the modifications made to the radiotherapy equipment to adapt to the various ocular tumors. Anticipation of the spectrum and severity of radiation-induced complications is crucial to the decision of which technique to use for a given tumor. Radiation can damage the lacrimal gland, eyelashes/eyelids, cornea, lens, macula/retina, optic nerves and chiasma, each having specific dose–response characteristics. The present review is a report of non-cancer effects that may occur following ionizing irradiation involving the eye and orbit and their specific patterns of toxicity for a given radiotherapy modality.
Highlights
Ocular tumors present ophthalmologists and oncologists with rare but various clinical situations
While the dose is usually expressed in Gy, a corrective radiobiological factor is necessary with particle therapy to account for increased linear energy transfer (LET) and increased radiobiological effectiveness (RBE) [4]
Ultra-high dose rate FLASH radiotherapy is a disruptive form of radiotherapy that might be used in single fractions; it does not rely on the geometry of dose distribution nor on temporal fractionation to achieve differential repair efficiency between normal and tumor tissues but rather on dramatically different radiochemistry that exploits normal tissue oxygenation to reduce normal tissue effects [11,12]
Summary
Ocular tumors present ophthalmologists and oncologists with rare but various clinical situations. The challenges include tumor control, as it often influences survival; organ (usually the eyeball) preservation; and the minimization of iatrogenic damage of sensitive tissues surrounding the tumor in order to preserve vision [2,3]. These aims should contribute to maintain the patient’s quality of life and should ideally translate into lower societal costs. The physics (along with their underlying radiochemistry and radiobiology) and technical aspects of radiotherapy are designed to deliver the prescribed dose in such a way as to avoid or minimize the amount of radiation delivered to nearby normal tissues while maximizing the dose delivered to the tumor This underpins the concept of a therapeutic risk/benefit ratio that attempts to strike a balance between complications and tumor control in a given situation. This anatomic area harbors a number of substructures of dramatically different tissue architecture and cell components, which determines their post-radiation fate
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